1-95
Figure 1-35.—Fiber optic symbols.—Continued.
Frequency Spectrum Designation
The complete spectrum of communications frequencies is broken down into ranges or bands. The
United States practice is to designate a two- or three-letter abbreviation for the name. The practice of the
International Telecommunications Union (ITU) is to designate a number. Table 1-25 shows the bands and
their designators. Table 1-26 indicates the frequency spectrum broken down as to usage.
Table 1-25.—Frequency Spectrum
FREQUENCY
DESIGNATOR
IUT
DESIGNATOR
BELOW 300 Hz
ELF (EXTREMELY LOW FREQUENCY)
--
300 Hz - 3 kHz
ILF (INFRA LOW FREQUENCY) SOMETIMES
VF (VOICE FREQUENCY)
--
3 kHz - 30 kHz
VLF (VERY LOW FREQUENCY)
4
30 kHz - 300 kHz
LF (LOW FREQUENCY)
5
300 kHz - 3 MHz
MF (MEDIUM FREQUENCY)
6
3 MHz - 30 MHz
HF (HIGH FREQUENCY)
7
30 MHz - 300 MHz
VHF (VERY HIGH FREQUENCY)
8
300 MHz - 3 GHz
UHF (ULTRAHIGH FREQUENCY)
9
3 GHz - 30 GHz
SHF (SUPERHIGH FREQUENCY)
10
30 GHz - 300 GHz
EHF (EXTREMELY HIGH FREQUENCY)
11
300 GHz – 3 THz
THF (TREMENDOUSLY HIGH FREQUENCY)
12
